DE2160661B2 - Tuning device for television receivers - Google Patents

Description

2. Tuning device according to claim 1, characterized in that the electronic switch has at least one transistor (TA ₁ , TR ₁ ; 14).

3. Tuning device according to claim 2, characterized in that the base-emitter path of the transistor (TA ₁ ) is connected in parallel with the motor (M) of the channel selector and the predetermined potential for the retuning lock is tapped from its collector.

4. Tuning device according to claim 3, characterized in that the collector of the transistor is connected to a connection point between the automatic retuning circuit (A) and the tuning element (V) of the channel selector (F i g. 1).

5. Tuning device according to claim 3, characterized in that the collector of the transistor (TA ₁ ) is connected to the junction of the retuning circuit (A) with a DC voltage source (E ₂ ) supplying the retuning circuit with voltage and the emitter of the transistor is grounded (F i g. 3).

6. Tuning device according to claim 3, characterized in that the collector of the transistor (TR ₁ ) is connected to the connection point of the retuning circuit (A) and the intermediate frequency amplifier and the emitter of the transistor is grounded (F i g. 5).

7. Tuning device according to claim 2, characterized in that the collector-emitter-S section of the transistor (TA ₁ ) is connected between the retuning circuit (A) and a DC voltage source (E ₂ ) supplying it with voltage (F i g. 4) .

8. Tuning device according to claim 1 or 2, characterized in that the interrupter (SW ₂ ; 3) optionally the tapping of a positive or a negative potential from the DC voltage source (E ₁ , E ₁ ;, 1,2) of the motor « (M ; 4) the channel selector enables.

_{9 Tuning device according to claims 2, 3, 4 and 8, characterized in that transistors (TA 1} , TR ₁ ) responding to the connection point of the interruption (SW) with the motor (M) of the channel selector between control voltages of different polarities are connected ( Fig. 6).

10 tuning device according to claim, characterized characterized in that the connection point of the interrupter (3) with the motor (4] of the channel selector to the control electrode of the transistor serving as an electronic switch (14) via a control circuit (6 to 13) mii another transistor (7) is connected. whose collector-emitter path is part of a connected to the control electrode of the transistor (14) serving as an electronic switch Voltage divider (7,8,9) is (F i g. 7 to 10).

U tuning means according to any one of claims 1 to 10, characterized is DAC additionally connected to the control electrode of the electronic switch (14) and this ansteuerndei in the sense of Nachstimmsperre provided manually operable switch (21) (FIG. 8 to 10).

12 Tuning device according to one of Claims 1 to 11, characterized in that the power switch (22) of the television receiver is also connected to the electronic delay circuit (11, 20, 29) via a delay circuit (11, 20, 29) which briefly excludes the effectiveness of the automatic retuning circuit (A) when the new switch is closed Switch (7,14) is connected (F 1 g. 8).

The invention relates to a tuning device for television receivers in the preamble of claim 1 specified Art., -__ "."

It is already known ("Funkschau" 1970, issue 21 S 745 ff) for travel receivers with electronic station search during the search in the VHF-Be rich to put the automatic frequency tuning de: VHF oscillator out of operation so that di < ZF curve is unique. A motor is provided for the search run, the tuning elements, for example Rotary capacitors operated. If the transmitter is found during the search, a control signal the motor drive is interrupted and the motor is quickly stopped by an electronic brake. Same The retuning lock is released in good time so that the captured transmitter is always optimally off remains in tune.

TV receivers are also equipped with an automatic retuning circuit (automatic / ine / uning = AFT). The automatic Nachstimmschal tune affects capacity variation diodes, which are used as Ab Vocal elements are used in the channel selector Here, too, it is uncomfortable when choosing a channel complicates the channel selection if the automatic «post-tuning circuit during the channel selection the Ka Capacity variation diodes of the channel selector further be influenced. It is therefore necessary and known that di < automatic retuning when switching over

3 ₄ T

, wipe channels bCT ,. when the device is tuning V ame Nachstiminsperre except Betneb to remov- particular channel is tuned to an aad, whose reception is desired, _m ea. This is done herkommlicherweise by a corresponding voltage by a Kanalwäbldaß as a channel selector which takes drive from circuit SL the down channel selecting circuit SL "and also be driven by a motor 5, can be used for the channel selection by a motor M angetrie- _Λ, is eme Schalteinnchtting use, ben. There is also an automatic retuning switch to switch between different channels.

The channel selector is thereby complicated and Fig. 2 shows the AFT circuit A depending on

expensive. io speed generated by the tuning frequency f.

! The object of the invention is, therefore, to provide a This follows the curve α of FIG

j, to create thnineumchtung for television receivers, frequency from / ₀ , the AFT circuit A delivers one - the at. Actuation of the channel selector to the simplest voltage that corresponds to this deviation. In this way, the retuning circuit for voltage is automatically given to the tuning element V of the channel. In Figure 2, moreover, a nenden part of claim 1 specified invention reference voltage E _{0 is entered} as curve b . Under certain circumstances resolved, the voting

It can be seen that here a special operation V of the channel selector instead of one of the curve a ent to achieve the retuning lock is not necessary ao speaking retuning voltage is frequency-independent. It is rather sufficient that by closing the independent fixed reference voltage E _{0 is} given. The zu-! ' Breaker in the supply circuit of the motor for the channel relationships will be explained in more detail in a moment. selector a channel selection process is initiated. The AFT circuit A also has, as shown in FIG.

at the same time results in a connection that shows two input terminals T ₁ and T ₂ . The control electrode of the electronic switch, the input terminal T ₁ is with a direct voltage, preferably a transistor with the direct voltage source E. "The input _{terminal T 2} with the IF-Vers, voltage source of the motor for the channel selector. The stronger connected so that at the input terminal; Control electrode, so for example the base of the T _{2 of} the IF image carrier is located.

; The transistor is thus at a certain potential The connection of the retuning circuit A with

brought and thus operated the electronic 30 to the tuning element V of the channel selector takes place switch to which it belongs. This thus provides a retuning lock on the one shown in FIG. 1, through which a type: The output voltage of the retuning point of the retuning circuit or a point of device A is via a series connection of resistor connection of the retuning circuit with the outlets A ₂ and R ₃ to the voltage input terminal the tuning element of the channel selector is placed on a fixed Poten- 35 voting element V. At the junction tial is brought. It can be, for example, the resistors R ₂ and R ₃ is the collector of a ground potential or the potential of a fixed transistor TR _x , the emitter of which is connected to a voltage source. Numerous practical embodiments connected to the source for the reference voltage E ₀ are possible: So this is possible. The DC voltage supplying the reference voltage E, the connection of the retuning circuit to the voltage source, is grounded on one side. The transistor is disconnected from the tuning elements or ineffective normally non-conductive so that the retuning is made. Instead, it is also possible to interrupt the circuit A for an automatic retuning connection of the retuning circuit with its direct voltage source of the tuning element V of the channel selector and so can. If, however, a control signal is applied to the base of the transistor TA ₁ by switching off the automatic retuning 45 via a resistor R ₁ and the transistor is switched on for an effective retuning block, then the hidden concern becomes. Finally, it is also possible to separate the connection point of the resistors R ₂ and R ₃ on frequency amplifiers by connecting the retuning circuit with the intermediate frequency collector-emitter path of the transistor TA ₁ . In any case, the reference voltage E _{0 is} maintained and thus a retuning lock is achieved in the simplest way, 5 ° retuning lock is effected.

without any additional operating control signal causing the retuning lock

Process or special effort is required of the base of the transistor TR ₁ from a control unit. In addition, the retuning lock is automatically supplied to the signal source. This is canceled when the channel selection is finished and the following: To initiate the channel selection, it is necessary to open the motor of the channel selector by opening the company connecting the motor M of the channel selector to its DC voltage source in operation. This is shut down with a DC voltage breaker. source E ₁ connected via a breaker 5W ₁ . In the drawing the invention is, for example, If the switch SW ₁ is closed, as is illustrated damil, also the supply circuit of the motor M is closed, and Fig. 1, the circuit of an embodiment of 60, the channel selection circuit SL in accordance with the Ka invention nalwahl in function. If the desired channel is selected in FIG. 2, a voltage-frequency characteristic curve is selected, the interrupter 5W _{1 is} opened and the method of operation of FIG. 2 is explained. 1 and thus also the supply circuit of the motor M interrupted F i g. 3 to 10 further embodiments of the Erchen, ie the motor is stopped. It is clear that this is the discovery. 65 Function with a motorized channel selector ii F i g. Figure 1 shows a tuner with each case required. The control signal source channel selector, which has a Tu- as the tuning element V , is therefore not a specially designed one with capacitance variation diodes. Addition provided for the purpose of the retuning lock

borrowed circuit. Rather, an interrupter SW ₂ is now used as a control signal, which source a circuit part that is required in any case, enables the motor M of the channel selector to run in advance, upwards and backwards by the Mo-Die on a channel selection process coordinated gate M Optionally to a DC voltage source E ₁ retuning lock works as follows: If 5 is closed for a positive voltage or to a DC voltage interrupter SW, and a channel source E ₁ 'for a negative voltage is thus initiated, a selection process is initiated at the same time. Correspondingly, the electronic also sees the resistor R ₁ at the base of the transistor TR ₁ , a switch made up of two transistors TR ₁ and TR ₁ , each of which base-emitter path to the motor M work in parallel as the transistor TR ₁ of FIG. 1 , is switched, the voltage of the DC voltage io whereby jsdoch the transistor TR _{1 is placed} when the source E _{1 is switched over} and the transistor switch SW _S, which has been blocked up to now, is conductive for connecting the motor M TR _{1 to it.} As a result, the connection to the DC voltage source E _{1 is} controlled to be conductive point of the resistors A ₂ and R ₃ on the reference, the transistor 77 ?, 'when the interruption _{voltage E n is switched} and the automatic follow-up SW ₂ to Connection of the motor M with the tuning circuit thus for the time of the channel selection 15 DC voltage source £ ','.

gangs made ineffective. The channel selector can thus Fi g. 7 shows a major modification of FIG. 1

unambiguously and undisturbed via the channel selection circuit or the FIG. 6. The control signal source again consists of SL tuning the tuning element V to a desired one from a DC voltage source 1 corresponding to the channel. As soon as the desired channel is selected from the DC voltage source E _t and one opposite, the switch SW ₁ is opened again. The polarized DC voltage source 2 corresponding to the base potential of the transistor TR ₁ drops, the Tran DC voltage source E ₁ . An interrupter 3 is locked and the retuning lock thus speaks to the interrupter SW ₂ of Fi g. 6. He is twofold. The automatic retuning circuit see the DC voltage sources 1 and 2 on the one hand acts again on the tuning element V of the channel selector and the motor 4 of the channel selector on the other hand. ^a 5 switches. The motor 4 can F i g in both directions of rotation. 3 shows a modified embodiment. circulate, depending on which of the two Here is the collector of the electronic switch DC voltage sources 1 and 2, it is connected to the input terminal breaker 3 via the sub-serving transistor TR _1. For this purpose, the DC of the AFT circuit A is connected, to which the DC voltage source 1 is connected to the negative pole and at the voltage source E _{2 is} connected. The emitter 30 DC voltage source 2, the positive pole as well as the transistor TR _1, is grounded. If a channel is now grounded, like the motor 4. The connection point of the dialing process by closing the switch SW ₁ switch 3 with the motor 4 is re-introduced and thus at the same time the transistor TR _{1 would be} S and 6 with the base of a controlled as electronic conductive , the input terminal T ₁ switch serving transistor 7 is connected, whose grounded and thus the automatic Nachstimmschal- 35 emitter is grounded via a resistor 8, wähtung put out of operation. The channel selection can thus be carried out easily and safely through the collector of the transistor 7. the stand 9 connected to a collector terminal 10 F i g. 4 shows a further modification of the embodiment. With the collector terminal 10, the base is approximately the form of Fig. 1. In this embodiment of the transistor 7 verbunflies through a resistor M through the excitation coil of the motor M current to 40 den. A diode 12 is used to base the transistor TR ₁ negative voltage when the breaker from the DC voltage source 2 to the base of the Tran-SW is open. The transistor TR ₁ is therefore to be conducted at offe- sistor 7 or the positive voltage from the interrupter SW _{1 is} conductive and in this case places the DC voltage source 1 to be earthed. Furthermore, the DC voltage source E ₂ prevents, via its collector, the diode 12, that the current flowing through the resistors 6 and to the input terminal 7 ″ of the 45 H, which generates a positive bias voltage so that the automatic after- for the base of the transistor 7, If the lower gate 4 is reached, which could disturb its operation, the breaker SW ₁ for initiating a channel selection process is also closed next to the diode 12, so the base potential of the oil is shown be provided with a diode 13, the verhinsistors TR ₁ is further increased, and transistor TR ₁ DA s' changed, that the negative voltage from the Gleichspanmit locked. the connection from the DC voltage source 2 to the emitter of the transistor 7 genungsquelle e ₂ This interrupts the AFT circuit A. At the same time, through the diode 13, the automatic retuning alarm is achieved that the positive voltage from the DC voltage source is not in operation e 1 is present at the emitter of transistor 7. Closing Fig.5 shows a third modification of the execution 55 borrowed prevents the diode 13 that the motor 4 through

it than the positive lying at the emitter of transistor 7 ?, is adversely affected by tension. The basis of one Another transistor 14 is connected to the collector of the r, like transistor 7. An AFT circuit 15, on which-

in the Atisführungform according to Fig. 1. the transistor 60 sen input terminal 16 the output of the IF amplifier TR ₁ conductive, when the motor M for a channel kers is connected with the motor 4 driven selection process is in operation. In this case, the tuner 17 (corresponding to the channel selection circuit SL input terminal T _t grounded and thus the IF picture element and the tuning element with the capacitance variation carrier are no longer fed to the AFT circuit A. The diode V) is connected via a resistor 18. The retuning lock is ensured again for the duration of the channel 65 collector of the transistor 14 is connected to the connection selection process. point of resistance 18 with the tuner 17. Dei

F i g. 6 shows a further embodiment in which the emitter of the transistor 14 is connected to a DC voltage instead of the interrupter SW ₁ of FIGS. 1 to 5 voltage source 19 connected, which has a positive reference

voltage E ₀ and its negative pole is grounded.

The embodiment operates as follows: the tuner 17 is on a desired channel matched and the interrupter 3 in the circuit shown in the figure, the motor 4 so out of order so will the base of the transistor? through resistors 6 and 11 on one kept constant preload. The transistor? is conductive and therefore acts as an electronic switch serving transistor 14 blocked because its base potential has dropped. The output of the AFT circuit 15 is thus connected via the resistor 18 to the capacitance-varying diode provided in the tuner 17, so that an automatic retuning takes place to ensure the reception of the set channel.

A channel selection process is now established by moving the interrupter 3 to the DC voltage source 1 initiated, the motor4 rotates, for example, clockwise, so that a higher frequency channel is chosen. The voltage coming from the DC voltage source 1 passes through the diode 13 to the resistor 8. The potential of the emitter of the transistor? is raised with it. To this Way will the transistor? conductive and thereby also the transistor 14 is controlled conductive. Similar to above with reference to FIG. 1 explains the automatic retuning circuit for the Zeilraum the channel selection without affecting the tuner 17, which means that the desired new channel can be accessed without interference can be matched. The retuning lock is thus reliably achieved.

A retuning lock is also achieved if the interrupter 3 is turned over to the side of the direct current source 2, so that the motor 4 rotates counterclockwise and selects a lower frequency channel on the tuner 17. Here the negative voltage of the DC voltage source 2 reaches the resistors. ¹ ) and6 to the base of transistor7, which is thereby blocked. This simultaneously turns the transistor 14 on, which in turn ensures the retuning lock for the duration of the channel selection process in the manner described above.

Regardless of the direction of rotation of the motor, it is automatically and simultaneously with the initiation of a channel selection process, the automatic retuning circuit is taken out of operation and thus facilitating the channel selection. There are no unpleasant repercussions.

F i g. FIG. 8 shows a further embodiment which is a modification of that of FIG. In this embodiment , a Nachstimmsperrc is achieved automatically as soon as the motor 4 is started to change the selected channel . In addition , the retuning lock is also kept in function for a certain period of time after the power switch has been closed, in order to ensure that in this case too, when the device is put into operation , it can be matched reliably to the channel that has just been set .

For this purpose, the circuit of FIG. 8. the we sentlichen with that according to F i g. 7 matches.

Equipped with some additional elements: A power connection 23 and a power switch 22, as well as one Mains circuit P (rectifier and filter circuit) are regarded as part of the control signal source. With the output of the mains circuit P is the resistor via a resistor 29 in the manner shown 11 connected. At the connection point of the resistor 29 with the resistor 11 is a grounded Capacitor 20 connected. There is also an additional switch 21 in the connecting line of the Interrupter 3 or the motor 4 connected to the resistor 5. The moving contact of the switch 21 can optionally rest on one of two fixed switch contacts 24 and 25, of which the Switching contact 24 with the direct current source 1, the switching contact 25 with the motor 4, d. H. with the movable Contact of the breaker 3 is connected. The moving contact of the switch 21 is located is normally in contact with the fixed switching contact 25. If the breaker is in its in the position shown in the figure, so if a channel selection does not take place, then the above with reference to F i g. 7 explained way so that the automatic retuning circuit in operation. However, it becomes the movable one Contact of the changeover switch 21 to the fixed switch contact 24 thrown back, so the voltage the DC voltage source 1 placed on the retuning lock, so that the automatic retuning circuit is independent of the position of the interrupter 3 without affecting the tuner 17.

The resistors 11 and 29 act with the capacitor 20 as a delay circuit: If the network switch 22 is closed, the increase in the potential at the base of the transistor 7 is determined by the time constants of this delay circuit. On the other hand, the transistor is connected to the mains voltage via the resistor 9 without delay. The transistor is thus conductive and, as a result, the transistor 14 serving as an electronic switch is also made conductive until the potential at the base of the transistor 7 has reached a certain threshold after the mains switch 22 has been closed. Only then is the transistor 14 blocked again. After the net switch 22 has been closed, the automatic retuning circuit remains for a certain time without affecting the tuner 17, which can thus be tuned to the set channel without errors. Once the tuning has taken place, the transistor 14 is blocked automatically, namely after the time determined by the time constantc of the VeT delay circuit, and the AFT circuit 15 is thus connected to the tuner 17, so that automatic fine tuning to the selected channel he follows.

9 and 10 show other possibilities of accommodating the changeover switch 21 for the compulsory deactivation of the automatic retuning circuit or for the compulsory retuning lock by hand in the circuit . The figures are self-evident. The circuits shown can be equipped with an automatic retuning lock according to FIG. 8 can be combined.

In addition 7 sheets of drawings

509511 / »

Claims (1)

Patent claims: 1. Abstract device for television receivers with a channel selector driven by a motor, which has a tuning element that determines the tuning frequency as a function of the voltage applied to it or the current flowing in it, with a DC voltage supplying the motor of the channel selector with voltage. > Voltage source, with an interrupter connected between the motor and the DC voltage source, with an automatic retuning circuit and a retuning lock which interrupts the effect of the retuning circuit on the tuning element of the channel selector when the channel is selected, characterized in that at the connection point between the motor (M, 4) of the Channel selector and the interrupter (SfF ₁ , SW _Z ; 3) the control electrode of an ao electronic switch (TR ₁ , TR ₁ '; 14) is connected and that when initiating a channel selection process by closing the interrupter and corresponding control of the electronic switch this one point the as Nachstimmsch aging (A, IS) or a point (of a connection with the tuning element (V) of the channel selector as a retuning lock at a predetermined potential.